This invention relates to a trimming copying machine and more particularly to a copying machine capable of preventing an enlarged image from sticking out of the copy paper position when only a specified area of an original document is copied.
There have been known trimming copying machines capable of copying only a specified portion of an original document and also those capable not only of trimming but also of enlargement and reduction. With a conventional trimming copying machine, however, the enlarged image of a specified area frequently sticks out of the copy paper position and this occurs especially when the specified area is near the backward edge of the scanned range. This is illustrated in FIG. 5 wherein G indicates an original document to be scanned in the direction indicated by the arrow .alpha., g.sub.1 and g.sub.2 respectively indicate the starting position and the end position of the scan and L indicates the width of the document G in the direction of the scan. Let us assume that a rectangular area A is to be copied with magnification M. The sides of the specified area A proximal to the starting position g.sub.1 and to the end position g.sub.2 of the scan (the left-hand and right-hand sides in FIG. 5) are indicated respectively by a.sub.1 and a.sub.2 and are hereinafter also referred to as the forward edge and the backward edge, respectively. The distance between the starting position g.sub.1 of the scan and the forward edge a.sub.1 of the specified area A is indicated by l and that between the starting position g.sub.1 and the backward edge a.sub.2 of the area A is indicated by l'.
With a conventional trimming copying machine, not only the specified area A but also the distances l and l' of its boundaries from the starting position g.sub.1 of the scan are magnified by the same factor M. Thus, if B indicates the enlarged image of the specified area A, its forward edge b.sub.1 is at a magnified distance lM from the starting position p.sub.1 of the scan on the copy paper P and its backward edge b.sub.2, likewise, is at another magnified distance l'M from the starting position p.sub.1 of the scan. If the dimension of the paper P in the direction of the scan is also L and if L is smaller than l'M, the image B sticks out of the copy paper position and the protruding portion of the image becomes lost. With a trimming copying machine of a conventional type, therefore, a larger copy sheet is sometimes required to be used.